Commutator riser construction



3,274,413 ADRIANCE, JR., ETAL. Sept. 20, 1966 r R Sept. 20, l966 T. R. ADRIANCE, JR., ETAL 3,274,413

COMMUTATOR RISER CONSTRUCTION Filed Deo. 4, 1963 2 Sheets-Sheet 2 /4 FIG, Z

INVENTOR EDWARD P. SMITH THEoDoRE R. ADRIANCE m United States Patent O v 3,275,413 COMMUTATOR RISER CONSTRUCTIGN Theodore R. Adriance, Jr., Delanson, and Edward P. Smith, Schenectady, N.Y., assignors to General Electric Company, a corporation of New York Filed Dec. 4, 1963, Ser. N0. 327,922 6 Claims. (Cl. S10- 234) The invention described herein rela-tes to dynamoelectric machines and particularly to an improved commutator riser construction useful in carrying current between commutator segments and coils mounted in slots on the armature peripheral surface.

The commuta-tor riser constructions conventionally used in large direct current machines generally comprise a multiplicity of radially extending ilat copper strips, each attached at one end Ito a commutator segment and at its other end to leads extending axially outward from corresponding coils in the armature. These riser strips vary in length depending on the machine size and distances of 20 to 30 inches between the commutator segments and the coil leads 'are not uncommon. During Vmotor operation, the riser strips are subjected to mechanical, magnetic and centrifugal forces, such that the ltotality of the-se forces, and particularly the mechanical impact stresses and stress amplification due to resonant frequenices generated in the complete riser construction, ycause fracture of the risers at their point of connection to the armature lsegments.

Many designs have been employed tolovercome these problems, such as securing discs of insulating material between the adjacent riser strips, tying and securing the strips `in spaced relationship with each other, .and still other well known constructions useful for imparting rigidity to the riser strip assembly, all for minimizing the Aadverse effects caused by the vibratory forces. One known successful solution to this problem is found in the invention disclosed in Goss et al. Patent No. 2,994,005, entitled Commutator Riser Construction and assigned to the same as-signee as the present invention.

In the Goss et al. design, the risers are sha-pcd to a parabolic cross section and a resin treated glass rope is installed at the risers at approximately the midpoint of their radial length for minimizing the establishment of Iresonant frequencies in the individual riser strips. In addition to this, fthe void spaces between adjacent risers at the point where they connect to the commutator segments are filled with an initially viscous or putty-like elastomeric material which cures to a relatively hard substance. The modulus of elasticity of the material is chosen to be compatible with that of the risers, preferably less, to which it is bonded to have it absorb the vibratory forces and thus minimize their application to the brazed joint of the risers and segments. By utilizing this kind of material and locating it near the brazed joint, a gradual transfer of stresses is made possible between the risers and segments, rather than the direct application of such stresses between these parts where the forces suddenly drop from a maximum to a minimum value. This construction has proved successful in operation but the primary disadvantage resides in the cost necessary t-o overcome the problems discussed above.

An additional problem presented by both the prior art and the Goss et al. construction, is that commutator risers form a barrier between the commutator and the other parts of the machine located behind the riser-s, thus making those parts inaccessible for maintenance and repairs. As is well known, this area of the motor gathers carbon dust and -other dirt particles which serve as current creepage paths to ground. In those cases where the degree of buildup of foreign matter is great, ashover 3,2 74,413 Patented Sept. 20, 1966 ICC between electrical parts operating at different potentials may occur, thus resulting in damage to the machine.

The primary object of our invention therefore is to eliminate the disadvantages inherent in the conventional commutator riser constructionsdiscussed above by providing a multiplicity of highly flexible leads interconnecting the commutator segments with current carrying coils in the armature.

In carrying out our invention, we interconnect the segments of a commutator with their corresponding coils in a motor armature with exible conductors capable of absorbing the stresses due Ito the impact and the amplification due to resonant vibratory frequencies usually encountered in large direct current motors and generators. To provide convenience in the assembling and subsequent maintenance of the equipment, the riser conductors serving separate groups of coils in the armature are assem-y bled and installed in the rotor as a unit thus minimizing the costs normally associated with this part of the manufacturing operation. It will be apparent to those skilled in the art that other riser constructions having leads of sufcient flexibility to permit assemblying them into groups may be used if desired.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject mat-ter which we regard as our invention, it is believed the invention will be better understood from the following description taken in connection with the accompanying drawings in which:

FIGURE l is a 'view in elevation of a portion of a direct current motor illustrating the disposition of riser conductors interconnecting commutator segments and the corresponding coils in the armature; and

FIGURE 2 illustrates the manner in which the risers are attached to a commutator segment and its corresponding coil leads.

Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout the several views there is shown a direct current motor comprising a commutator 8 supported on a shaft (not shown) and a spider having outwardly projecting arms which support a magnetic core for an Iarmature 10, and having slots disposed in its peripheral surface for accepting coils 12 in a manner well known in the art.

The commutator 8 consists of a multiplicity of commutator segments 13 of a well known design arranged to be :secured to the motor shaft. As shown in FIGURE 2, each commutator segment 13 has a bottom portion .14 ladapted for attachment to the shaft, while the upper surface 16 is finished for -contact by carbon brushes. Each segment includes a V-shaped notch on one end adapted for engagement =by a commutator flange or hub 18 which serves to holdall the segments .in position and likewise is secured to the shaft of the machine. An outwardly projecting ltab 20 integrally formed with each commutator segment is equipped with a saw slot 22 designed to receive the flattened end of a commutator riser 23, the parts being joined together, as by brazing. As in conventional designs, insulation 24 electrically isolates the hub 18 from the segments 13. Also, separate cylinders of glass tape 25 and 26 impregnated with a thermosetting resinous com-position which cures to a hard rigid substance :are wound on the peripheral surface of the tabs 20 and the risers 23 for respectively holding the segments and the risers and equalizer leads (not shown) against displacement when the armature is related.

Each of tabs 20 shown in both figures are of substantial axial length and are insulated from each other by the same insulation 27 used for electrically isolating adjacent commutator segments from each other. Although L- shaped commutator segments are shown, it will be apparent that many other designs of segments may be used, with or without outwardly projecting tabs, for accepting the ends of the commutator riser conductors.

The riser conductors 23 are chosen of a size sufficient to carry the currents expected to be encountered during operation and preferably are of circular cross section. As shown in FIGURE 2, the riser extends axially inward from the commutator segments 20, then radially outward Vfor connection to leads extending from the coils 12 located in slots disposed in the armature surface.

Sin-ce the size of machine chosen to illustrate the invention is a large direct current motor Iof about 4500 h p., a -pair of coils 12 are located inV each of the rotor slots and terminate in the end turns shown extending axially outward therefrom. Copper `strips 28 are brazed to the sides of the end turns and insulation 30 is disposed between -adjacent strips and therefore the coil conductors for electrically isolating them from each other.

Because the riser conductors are flexible, they are bent at an approximately 90 angle axially outward to a point adjacent each of the strips 28 where they lie in a position to be brazed convenient-ly to the stri-ps. To minimize displacement of the strips attached to the coil end turns, a rim 34 preferably of metal is placed in contact with the strip inner peripheral portions and is secured to the rotor spider by bolts 36. Other forms of this construction for minimizing strip displacement may be used such as binding, tying, or clamping the strips in an immovable position. Also, to prevent displacement of the coil end turns outwardly, insulation 38 and a multiplicity of turns V4of glass tape 40 treated with an initially viscous thermosetting -composition is wound over their outer peripheral surface. When the resin is cured to a hard rigid substance, the resulting bandl is effective in preventing end turn dis- -placement in a manner well known in the art.

In order to make the inner parts of the motor accessible formaintenance and repair and for permitting accessibility to all those areas having current carrying parts, each group of commutator risers are located within a housing 42 of rectangular configuration, long enough -to bridge the distance between the commutator and the coil end turns. The housing preferably comprises a hard insulating material, such as that identified by the trademark Textolite, and after the risers are placed therein, the sides of the housing are assembled and taped together to form a unitary structure. Since the armature rotates at relatively high speeds, it is necessary to firmly anchor the housing with its risers to the armature spider slots 44 and this is accomplished by the simple use of brackets 46 and bolts 48. Obviously, each group of risers may be taped or otherwise assembled together and anchored to stationary parts of the armature.

After the process of connecting -a commutator riserto its corrsponding commutator segment `and coil lead is completed, the s-paces between adjacent tabs on the commutator segments are filled with a resinous composition 50 capable of curing to -a hard rigid substance. As previously indicated, before curing takes place, the outer peripheral surf-ace of the commutator segment tabs is wrapped with a glass tape impregnated with a thermosetting resinous composition which is cured at the same time as the other resinous materials. When cured, the glass tape restricts radial displacement of the commutator segments and the inner portion of the connections when the armature is placed in operation.

In lieu of extending the insulation between adjacent commutatorsegments outwardly to a point between the adjacent tabs, it may be cut off at the commutator segment surface and the tabs then insulated from each other by being encapsulated with the same resinous composition described above. Many different kinds of resins may be used for this purpose including polyester, epoxy and other types which have the necessary and obvious characterlistics of being bondable to the copper of the metal strips,

or the insulation when it is used, having a reasonable modulus of elasticity, easy to handle and capable of being cured preferably in the same temperature range as the conventional varnish applied to the motor armature during a final dip and bake cycle.

Since the objective is to minimize and preferably completely eliminate the stresses and resonant frequencies in the riser construction, it will be apparent the assembling of risers into separate groups may be eliminated. In this case, the risers emanate from the commutator and form a construction of spoke-like configuration and give the general appearance of the prior art designs. However, they do not extend in a straight line between the co-mmutator and coil end turns but are bent in a direction toward the armature where they are secured in position prior to extending in a general axial direction outwardly for attachment to the end turns. Any one of several obvious methods may be employed for attaching the risers to th-e spider plate, such as securing a circular-shaped bracket on the plate by welding. The leads then are attached to the bracket by resin treated tie cords of nylon, for example.

The particular advantages gained from employing this kind of construction, and which is primarily attributable to the riser conductor flexibility, resides in a reduction of stresses normally resulting from thermal expansion and shaft deflection. The resonant frequency of the assembled mass of risers is much higher than that of known constructions thus minimizing the effect of forced vibrations generated from a load to which the machine would be subjected, or from other connected machinery. The underside of the front end of the rotor coils at the connection end is now` radially accessible for cleaning thereby permitting maintenance which will increase the reliability of the machine. Moreover, additional freedom in axially locating the commutator with respect to the rotor end winding is now possible.

In view of the above, it will be apparent that many modifications and variations are possible in light of the above teachings. It therefore is to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically described.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A rotor for a dynamoelectric machine comprising: a shaft supporting a commutator and an armature having coils in slots disposed in its peripheral surface,

commutator riser-like connections interconnecting segments in t-he commutator ywith leads extending axially outwardly from the coils in the armature,

said riser-like connections comprising a multiplicity of exible conductors assembled into separate groups disposed radially around the commutator,

and means spacing each of said groups from the other to permit accessibility of those armature parts axially inward of the commutator for facilitating maintenance and repair.

l2. A rotor for a dynamoelectric machine comprising:

a shaft supporting a commutator and an armature having coils disposed in slots in its outer peripheral surface,

commutator riser-like connections interconnecting segments in the commutator with leads extending axially outwardly from the coils in the armature,

said riser-like connections comprising a multitude of flexible conductors respectively extending inwardly in a general axial direction from t-he point of their connection to the commutator segments and extending outwardly to the point of their connection with the leads for coils in the slots,

said riser-like connections being assembled into a plurality of groups disposed radially around the commutator,

means holding the risers in each of said groups into an integrated mass, and

means securing each of said groups of risers against displacement when the armature is rotated.

3. A rotor for a dynamoelectric machine comprising: a shaft supporting a commutator and an armature having coils in slots `disposed in its peripheral surface, commutator riser-like connections interconnecting segments in the commutator with leads extending axially outwardly from the coils in the armature,

said riser-like connections comprising a multiplicity of flexible conductors assembled into separate groups and thereby providing a plurality of groups of riserlike connections extending radially and spaced circumferentially around the commutator,

each of said riser-like connections being attached at one end to a tab-like projection formed on each commutator segment and at its other end to a metallic strip secured to the leads extending axially outwardly from a coil in the armature,

each of said groups of riser-like connections further being assembled into an integrated mass and secured to the armature for preventing their displacement when the armature is placed in operation.

4. A rotor for a dynamoelectric machine comprising: a shaft supporting a commutator and an armature having coils in slots disposed in its peripheral surface, commutator riser-like connections interconnecting segments in the commutator with leads extending axially outwardly from the coils in the armature,

said commutator comprising a multiplicity of individual segments having a projection on one end thereof and being spaced by insulation from a similar projection on the next adjacent commutator segment,

a banding tape wound on the outer peripheral surface of the projections for preventing commutator segment displacement during arma-ture operation,

said riser-like connections comprising a multiplicity of flexible conductors assembled into separate groups and each being attached at one end to a projection and at its other end to the corresponding lead for a coil in the armature,

said riser-like connections extending inwardly in a general axial direction from both the commutator projections and the coil leads,

means assembling the riser-like connections in each of said groups into an integrated mass, and

a bracket securing each of said groups of riser-like connections to said armature for preventing their displacement during armature operation.

5. A rotor for a dynamoelectric machine comprising:

a shaft supporting a commutator and an armature having coils in slots disposed in its peripheral surface,

commutator riser-like connections interconnecting segments in the commutator with leads extending axially outwardly from the coils in the armature,

said armature including a magnetic core for supporting said coils and including individual end turns projecting outwardly therefrom,

a metallic strip secured to each of said end turns,

said riser-like connections comprising a multiplicity of flexible conductors respectively interconnecting the commutator segments with the corresponding strips attached to the coil end turns,

said riser-like connections being assembled into a plurality of separate groups such that said groups extend in a radial direction and are spaced from each other circumferentially around the commutator, and

means securing each of said groups of riser-like connections to said armature for preventing their displacement when the machine is placed in operation.y

6. The combination according to claim 5 wherein a banding tape impregnated with an initially viscous thermosetting material is Wrapped around the outer peripheral surface of said end turns and cured to a hard rigid mass for preventing their displacement when the armature is rotated.

References Cited by the Examiner UNITED STATES PATENTS 587,871 8/1897 Short 310-265 2,298,862 10/1942 Balz et al. 310-265 2,683,827 7/ 1964 Letrilliart et al. 310-234 X 2,994,005 7/ 1961 Goss et al 310--234 3,073,980 1/1963 Hoover 310-234 MILTON O. HIRSHFIELD, Primary Examiner.

ORIS L. RADER, Examiner.

C. W. DAWSON, D. F. DUGGAN, Assistant Examiners. 

4. A ROTOR FOR A DYNAMOELECTRIC MACHINE COMPRISING: A SHAFT SUPPORTING A COMMUTATOR AND AN ARMATURE HAVING COILS IN SLOTS DISPOSED IN ITS PERIPHERAL SURFACE, COMMUTATOR RISER-LIKE CONNECTIONS INTERCONNECTING SEGMENTS IN THE COMMUTATOR WITH LEADS EXTENDING AXIALLY OUTWARDLY FROM THE COILS IN THE ARMATURE, SAID COMMUTATOR COMPRISING A MULTIPLICITY OF INDIVIDUAL SEGMENTS HAVING A PROJECTION ON ONE END THEREOF AND BEING SPACED BY INSULATION FROM A SIMILAR PROJECTION ON THE NEXT ADJACENT COMMUTATOR SEGMENT, A BANDING TAPE WOUND ON THE OUTER PERIPHERAL SURFACE OF THE PROJECTIONS FOR PREVENTING COMMUTATOR SEGMENT DISPLACEMENT DURING ARMATURE OPERATION, SAID RISER-LIKE CONNECTIONS COMPRISING A MULTIPLICITY OF FLEXIBLE CONDUCTORS ASSEMBLED INTO SEPARATE GROUPS AND EACH BEING ATTACHED AT ONE END TO A PROJECTION AND AT ITS OTHER END TO THE CORRESPONDING LEAD FOR A COIL IN THE ARMATURE, SAID RISER-LIKE CONNECTIONS EXTENDING INWARDLY IN A GENERAL AXIS DIRECTION FROM BOTH THE COMMUTATOR PROJECTIONS AND THE COIL LEADS, MEANS ASSEMBLING THE RISER-LIKE CONNECTIONS IN EACH OF SAID GROUPS INTO AN INTEGRATED MASS, AND A BRACKET SECURING EACH OF SAID GROUPS OF RISER-LIKE CONNECTIONS TO SAID ARMATURE FOR PREVENTING THEIR DISPLACEMENT DURING ARMATURE OPERATION. 